Automated system and method for optical measurement and testing

ABSTRACT

A system and method for bit error rate testing optical components comprises providing an optical testing unit, which measures a bit error rate of an optical device under test (DUT) over an operating range of the DUT. The optical testing unit includes an optical transmitter, which transmits an optical test signal that is transmitted to the DUT; an optical receiver, which receives an input signal from the DUT; a graphical user interface, which provides an interface with a user; and a controller, selectively coupled to the transmitter, the receiver and the graphical user interface, wherein the controller provides a central control of the transmitter, the receiver and the graphical user interface.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation under 35 U.S.C. § 365(c) and35 U.S.C. §120 from international patent applications PCT/US02/12816 andPCT/US02/12819, entitled “Automated System and Method For Performing BitError Rate Measurements On Optical Components”and “Automated System andMethod For Determining the Sensitivity of OpticalComponents,”respectively; and each being filed on Apr. 23, 2002. Theseinternational applications claim priority from U.S. provisional patentapplications 60/285,805 and 60/285,804, filed Apr. 23, 2001respectively. Thereby priority under 35 U.S.C. § 119(e) is claimed. Thepresent application is a divisional application of U.S. patentapplication Ser. No. 10/613,293 filed on Jul. 3, 2003. The disclosuresof each of the referenced applications are specifically incorporated byreference herein.

BACKGROUND

Optical components, including fiber optic cables, connectors,transmitters, receivers, switches, routers and all other types ofoptical components have become the backbone of the moderntelecommunication infrastructure. Due to their extremely low error rateand wide bandwidth, optical communication systems have supported anexplosion in the growth of data communication systems, such as theInternet. With the Internet in its infancy, it is expected that thereliance on optical components and systems will only increase as theInternet becomes more closely intertwined with mainstream business andconsumer applications.

Although the technology associated with optical communication systemsand components has greatly advanced over the last decade and the use ofsuch technology has accelerated, the technology associated with testingoptical communication systems and components has greatly lagged.

Bit error rate (BER) measurements are a standard tool in verifying theperformance of any digital optical communication system. Nevertheless,such tests remain an underutilized resource in understanding anddiagnosing issues with such systems; particularly with respect to thereceive-side optical front end. There are many contributing factors tothis situation; chief among them are a lack of hardware and softwareresources, the time consuming nature of such measurements, and a lack ofappreciation and understanding of the information content suchmeasurements can provide.

As is well known, the BER is given by the ratio of incorrectlyidentified bits to the total number of bits processed. In opticalsystems, BER tests are most commonly associated with determining thesensitivity of the optical receiver. Clearly, if the input optical powerdecreases enough, the receiver will begin generating errors. Receiversensitivity is the input optical power required for a particular BER.Sensitivity is typically measured in dBm where:

$\begin{matrix}{P_{dBm} \equiv {10\mspace{14mu}{\log\left( \frac{PmW}{1\mspace{14mu}{mW}} \right)}}} & {{Eqn}.\mspace{14mu}(1)}\end{matrix}$

Accordingly, 0 dBm corresponds to 1 mW. The result depends strongly onthe measurement conditions including the quality of the transmitter, theamount of input optical noise, the BER required, the data rate and thedata being transmitted. A typical measurement might involve a highquality transmitter, no added input noise, a well-defined pseudorandombit sequence and a required BER of 1×10⁻¹⁰.

For a network designer, sensitivity is often regarded as the mostimportant figure of merit for a receiver since it suggests a minimuminput operating power for the device. A designer would ordinarily planto operate the receiver with an input power high enough above the quotedsensitivity such that the expected error rate will not impact thereliability of the link. But how high above the sensitivity power levelthe receiver should be operated at is one of the fundamental questionsthat careful BER measurements can answer.

Due to the current state of technology for optical testing equipment,testing an optical component at many small increments of optical powerover the full operating range is not realistic. To wit, via currentpractices, in order to perform these measurements, it is often necessaryfor a technician first to set the optical power of the test equipment tothe desired optical power (which is an iterative process), and then mustseparately measure the number of errors at that optical power. Since thenumber of errors exhibited by optical equipment is extremely low, (i.e.,1×10⁻⁹ or less), it would necessitate a technician to continually attendto the testing equipment over a series of hours or days.

Known testing regimens avoid the problem of lengthy test procedures byrequiring a technician to measure the BER over a few discrete levels ofoptical power. These results are then extrapolated throughout the entireoperating range of the optical component to arrive at the behavior ofthe component over the entire operating range of the component.Extrapolating the results in such a manner increases the risk that thetrue behavior exhibited by the optical component at levels of powerbetween the measured discrete levels will be missed. This can lead tolater errors in the technical specifications for the particularcomponent.

What is needed is a simple and effective system and method for testingoptical components.

SUMMARY

According to an exemplary embodiment an optical testing unit measures aparticular parameter of an optical device under test (DUT) over anoperating range of the DUT. The optical testing unit includes an opticaltransmitter, which transmits an optical test signal that is transmittedto the DUT; an optical receiver, which receives an input signal from theDUT; a graphical user interface, which provides an interface with auser; and a controller, selectively coupled to the transmitter, thereceiver and the graphical user interface, wherein the controllerprovides a central control of the transmitter, the receiver and thegraphical user interface.

According to another exemplary embodiment, a method of measuring aparticular parameter of an optical component includes: providing anoptical testing unit; providing a test optical signal as an outputsignal to a device under test (DUT); receiving an input signal from theDUT; measuring the particular parameter from the input signal; andproviding a control unit which controls various components in theoptical test unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read with the accompanying drawing figures. It is emphasized thatthe various features are not necessarily drawn to scale. In fact, thedimensions may be arbitrarily increased or decreased for clarity ofdiscussion.

FIG. 1 is a block diagram of a testing system in accordance with anexemplary embodiment of the present invention.

FIG. 2 is a block diagram of a control unit in accordance with anexemplary embodiment of the present invention.

FIG. 3 is a flow chart of a calibration procedure in accordance with anexemplary embodiment of the present invention.

FIG. 4 is a flow chart of a test procedure in accordance with anexemplary embodiment of the present invention.

FIG. 5 is a block diagram of a control unit in accordance with anexemplary embodiment of the present invention.

FIG. 6 is a flow chart of a sensitivity test procedure in accordancewith an exemplary embodiment of the present invention.

FIG. 7 is a flow chart of a standard comparison procedure in accordancewith an exemplary embodiment of the present invention.

FIG. 8 shows a front view of a graphical user interface in accordancewith an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation andnot limitation, exemplary embodiments disclosing specific details areset forth in order to provide a thorough understanding of the presentinvention. However, it will be apparent to one having ordinary skill inthe art that the present invention may be practiced in other embodimentsthat depart from the specific details disclosed herein. In otherinstances, detailed descriptions of well-known devices and methods maybe omitted so as not to obscure the description of the presentinvention. Wherever possible, like reference numerals refer to likeelements.

Briefly, as described in connection with exemplary embodiments herein,the present invention relates to a unitary optical testing apparatus andmethod for performing measurement and testing of optical components.These measurements and testing are illustratively performed to determinethe sensitivity, or BER, or both of the optical components. Usefully, asingle control unit automates calibration and testing via the unitaryoptical testing apparatus. This automation enables a technician toperform the measurement and testing in a rapid, efficient and accuratemanner when compared to known measurement and testing schemes.

FIG. 1 shows a block diagram of an optical testing unit 100 inaccordance with an exemplary embodiment of the present invention. Theoptical testing unit 100 illustratively includes an optical transmitter150, an optical attenuator 152, an optical power monitor 154, an opticalreceiver 156, a control unit 158, an optical splitter 192 and agraphical user interface (GUI) 160. Illustratively, all of the opticalcomponents may be disposed in a housing 104. The optical testing unit100 may also include fiber optic cables 186, 188, 190, 194, 196 andoptical output and inputs 198, 199 between the optical testing unit 100and a device under test (DUT) 105.

The optical testing unit 100 of the exemplary embodiment is optimized byincluding a common control bus 184 and a common power bus 182, which iscoupled to a central power supply 180. Each active component 150–160within the optical testing unit is coupled to both the control bus 184,via a control (C) interconnection, and to the power bus 182 via a power(P) interconnection. This permits the elimination of redundant powersupplies and power feeds to each separate component, permits a singlecontrol bus to control all of the components 150–160, and eliminates allredundant user interfaces with each optical component.

A single control unit 158 is useful in the automated measurement andtesting of the DUT 105. Beneficially, having a single control unit 158providing selective control of each optical component 150–156 greatlysimplifies the testing procedure. For example, having a single controlunit 158 also permits calibration of the entire optical testing unitfrom a common point of control. This and other benefits will becomeclearer as the present description continues.

Illustratively, all of the optical components 150–156 are fixed in arigid spatial relationship. Also the optical cables 186, 188, 190, 194,196 are also rigidly fixed to prevent an inadvertent degradation orcomplete separation of an interconnection between optical components.

In the exemplary embodiments described herein, each of the opticalcomponents 150–156 may also include one or more optical interfaces. Forexample, the optical transmitter 150 may include an optical output 70.The optical attenuator 152 may include an optical input 72 and also anoptical output 74. The optical power monitor 154 may include an opticalinput 76, and the optical receiver 156 may include an optical input 78.The optical splitter 192 may include an optical input 93 and two opticaloutputs 95, 97. The housing 104 may include an optical output port 198and an optical input port 199. Illustratively, the optical output port198 is coupled with the input of the DUT 205 and the optical input port199 is coupled with the output of the DUT 205.

The control unit 158 may be configured to control the various componentsof the optical testing unit 100 in order to affect different types ofmeasuring and testing. In accordance with a first embodiment describedpresently, the control unit usefully enables BER testing; and in asecond embodiment described herein, the control unit usefully enablessensitivity testing and measurements. As can be appreciated, the typesof measurements and testing techniques controlled by the control unit158 disclosed via the exemplary embodiments are intended to beillustrative and not limit the scope of the invention. It is thus notedthat the control unit 158 may be configured to affect (via interactionwith various components of the optical testing unit 100) the trafficbeing generated (protocol, binary sequence, etc.), the traffic rate(i.e., bit rate), and the optical power (expressed in a variety of waysincluding, but not limited to, average optical power and OpticalModulation Amplitude). Using facilities within the optical testing unit100, the control unit 158 can also examine the signal coming from theDUT and determine the BER either by considering the traffic bit by bitor by examining any coding scheme embedded within the traffic whichprovides indications that transmission errors have occurred.

Referring to FIG. 2, the control unit 158 according to an exemplaryembodiment is shown in greater detail. The control unit 158illustratively includes a microprocessor 210, an input/output (I/O)buffer 212, and an associated memory 214. Microprocessor 210 should ofcourse be able to control various hardware and obtain data therefrom.The memory 214 permits storage of a plurality of individual softwaremodules, predetermined component test parameters and any otherinformation which is required to be stored by the control unit 158. Forexample, the memory 214 includes a calibration module 216 and a testmodule 218. The memory 214 may also include spare capacity or may beexpanded by adding additional memory capacity for future modules 220.Although these modules 216–220 have been shown and described as separatecomponents for ease of explanation in the present embodiment, it isnoted that this is merely illustrative. To wit, these modules areresident in software and the software may be stored, and the memory 214partitioned, as desired by the technician. Calibration module 216provides for the calibration of optical test unit 100 as a system, asopposed to each individual element 150–156. Test module 218 is aconglomeration of individual software algorithms that control thehardware within optical testing unit 100, record bit error rate data,analyze that data and display results of the analysis. The proceduresaffected by modules 216 and 218 will be discussed in detail later withreference to FIGS. 3 and 4, respectively.

Illustratively, data buses 222, 224, 226 affect the flow of data betweenthe microprocessor 210; the memory 214 and the I/O buffer 212. Anotherdata bus 228 facilitates the flow of data between the I/O buffer 212 andthe control bus 184. Alternatively, the data bus 228 may be deleted andthe I/O buffer 212 be coupled directly to the control bus 184 . Althoughthe microprocessor 158 is illustrated herein as including an I/O buffer212, in an alternative embodiment of the present invention, the controlunit 158 provides for direct access to the memory 214 such that the I/Obuffer 212 is not required. Of course, any accessing of the memory 214in that embodiment may be monitored and/or controlled by themicroprocessor 210.

The process implemented by the individual modules will now be describedin greater detail with reference to FIGS. 3 and 4. Referring initiallyto FIG. 3, a calibration procedure 300 in accordance with an exemplaryembodiment of the present invention is shown. This calibration procedureis useful in realizing BER measurements of the present exemplaryembodiment. There is a need to be able to calibrate the optical testingunit 100 via either internal or external means. It is preferable that itis calibrated as a system and not as individual units, such as theoptical transmitter 150 and the optical receiver 156. By calibrating itas a system, optical testing unit 100 is more accurately reliable than asystem made up of individually calibrated stand-alone components.

It is noted that similar calibration procedures with subject specificvariations may be used to calibrate optical testing unit 100 to realizediffering measurements and tests. Additionally, it is noted that thecontrol unit 158 can directly control external instrumentation tomeasure aspects of the transmitted or received signal to allowcalibration of the optical testing unit 100. Alternatively, measurementscan be made completely independent of the control unit 158 (eithermanually or under the control of an external computer) and subsequentlycommunicated to the control unit 158 to affect the calibration of theoptical testing unit 100.

It is noted that in order to calibrate optical testing unit 100, anexternal optical jumper (not shown) may be placed between the opticaloutput port 198 and the optical input port 199. This completes theoptical path between the optical transmitter 150 and the opticalreceiver 156. Alternatively, an internal optical switch 197 may beprovided to switch the output of the optical attenuator 152 to the inputof the optical receiver 156. Illustratively, optical switch 197 isautomatically controlled by the control unit 158 when the calibrationprocedure 300 is implemented. Alternatively, the optical switch 197could be manually operated. Use of the optical switch 197 is beneficialsince it eliminates the need for a technician to install an externaloptical jumper and eliminates any degradation problems caused by adamaged external optical jumper.

The calibration procedure 300 begins with the control unit 158retrieving pre-stored optical transmitter calibration parameters frommemory (step 302). The calibration parameters may be either predefinedvalues stored in memory by a technician; may be factory settings for theoptical components 150–160; may be the results of prior calibrationtests; or may be a combination thereof. The control unit 158 thenenergizes all of the optical components (step 304); and, after apredetermined duration, which permits the electronic components thereinto reach steady state, the control unit 158 measures the operatingparameters, which comprise the optical output power and the internal BER(step 306).

The control unit 158 then compares the calibration parameters to themeasured operating parameters (step 308). If the operating parametersare within a predefined range of the calibration parameters, the controlunit 158 stores the positive test results (step 310). If the operatingparameters are not within the predetermined range of the calibrationparameters, the system has failed the calibration procedure 300 and thecontrol unit 158 stores this failure 312. Preferably, as the controlunit 158 receives the test results, whether pass or fail, the controlunit 158 provides an output to the graphical user interface 160 to keepthe technician apprised of the results of the procedure (steps 314,316). If the system has failed, control unit 158 may (in conjunctionwith steps 312, 314 or in an additional step, not shown) adjust variousaspects of optical testing unit 100, store any necessary information inmemory 116, and may restart the calibration procedure at an appropriatestep, such as step 306. This may be repeated until the system haspassed.

It is noted that the steps 302–316 set forth in the calibrationprocedure 300 need not necessarily occur in the order set forth in FIG.3; and that other calibration sequences may be followed, which mayinclude the same number of steps, or more or fewer steps. For example,step 302 may occur between steps 306 and 308. Those of skill in the artwould clearly recognize that there is flexibility in the ordering ofsome of these steps. Additionally, step 304, which relates to theenergizing of the optical components, may be performed by the technicianupon powering up the equipment. Moreover, steps 310 and 312 may beeliminated, whereby the results of the calibration procedure 300 are notstored. These alternative calibration sequences are merely illustrative,and other sequences may be followed in keeping with the presentexemplary embodiment.

Once the calibration procedure 300 has been successfully completed, theoptical testing unit 100 is ready to test an optical component.Referring back to FIG. 2, in order to implement the test procedure 400,the microprocessor 210 accesses the test module 218. The test procedure400 is shown in greater detail in the flow diagram of FIG. 4. It isnoted that the test procedure 400 may be fully automated, whereby thetechnician initiates the process (e.g., pushes a ‘start button’) andpermits the control unit 158 to fully carry out the test procedure 400.Alternatively, the test procedure 400 may be selectively automated,whereby the technician may set certain parameters for the system totest. For example, the technician may set specific power levels for thesystem to test and may also set a specific number of errors, or range ofuncertainty, at each power level. In any event, the present exemplaryembodiment is implemented via the illustrative test procedure 400 shownin FIG. 4.

The test procedure 400 begins by the technician's initiating theprocedure (step 402). This can be as simple as the technician's pushinga “start test” button on the graphical user interface 160, or by thetechnician's setting forth all of the individual testing parameters andpushing a “start test” button. The optical transmitter 150 is energizedto transmit generally at a desired power level (step 404). Since theoptical transmitter 150 is unable to fine-tune its output power level,additional steps 406–410 using the optical power monitor 154 and theoptical attenuator 152 to iteratively fine-tune the output power levelare desirable. The optical power monitor 154 measures the output of theoptical transmitter 150 (step 406) and determines whether the outputpower level is at the desired power level (step 408). If the outputpower level is not at the desired power level, the optical attenuator152 is tuned to attenuate the output of the optical transmitter 150 asappropriate in order to more closely achieve the desired power level(step 410). The optical testing unit then uses the optical power monitor154 to again measure the output of the optical transmitter 150 (step406). Steps 406–410 are repeated until the output power level is at thedesired power level.

Once the desired power level has been achieved, the optical receiver 156measures the number of bit errors at that specific power level (step412). This step is performed until the “completion criteria” is met. Thecompletion criteria may be a particular duration, a particular number ofbit errors received, or attaining a particular uncertainty.

Regardless of which criteria is used to determine whether the testing iscomplete at that power level (step 414), the optical testing unititeratively and continuously repeats steps 412 and 414 until the testingis complete for that particular power level. Once the testing iscomplete at the particular power level, the optical testing unitdetermines whether the testing for all power levels desired to be testedhas been completed (step 416). If not, the optical testing unit adjuststhe power level to the new desired power level (step 418) and the entireprocess (steps 406–416) is repeated until the testing at all powerlevels has been completed. The results are then output to the graphicaluser interface 160 (step 420).

The testing procedure 400 has many advantages over prior testingmethods. First, because it is automated, optical testing unit 100 mayoperate autonomously without a technician having to perform all thefunctions manually. This saved time and effort.

Another advantage is that there are fewer uncertainties with testingprocedure 400 than with the prior methods. The fact that the opticaltesting unit 100 is a single system having rigidly fixed internalcomponents and optical cables yields less uncertainties with testingresults than a group of individual stand-alone components. This is sobecause the true accuracy of the group of individual stand-alonecomponents is unrealized because of all the loose interconnections.

Another advantage is that the test can proceed faster than individualstand-alone components automated with an external PC because all thecomponents 150–156 are directly under the control of the control unit158 and are built into optical testing unit 100 to work together.

Yet another advantage is that mathematical models of how BER shouldbehave as a function of optical degradations can be stored in memory 214and can be displayed to graphical user interface 160 in a meaningful wayif desired. Optical testing unit 100 is specifically built to measureBER as a function of various optical degradations.

As mentioned previously, another exemplary embodiment of the presentinvention relates to measurement and testing of sensitivity of opticalcomponents. The optical testing unit 100 of the exemplary embodiment ofFIG. 1 may be used to affect this type of measurement and testing.Accordingly, the common details of the various elements are not repeatedin the interest of brevity. It is noted that a significant differencebetween the exemplary embodiments drawn to BER measurement and testing,and sensitivity measurement and testing lies in the substance andcharacteristics of the control unit 158.

Referring to FIG. 5, control unit 158 in accordance with an exemplaryembodiment is shown. Control unit 158 of FIG. 5 is similar to that shownin FIG. 2. The control unit 158 includes a microprocessor 210, aninput/output (I/O) buffer 212, and an associated memory 254. The memory254, like memory 214 of FIG. 2, permits storage of all of the individualsoftware modules, predetermined standard success criteria (optional) andany other information, which is required to be stored by the controlunit 158. For example, the memory 254 includes a sensitivity test module256 and standard success criteria 258. The memory 254 may also includeenough room for future modules 220. Again, although these modules256–258 and 220 have been graphically illustrated as separate componentsfor ease of explanation in the present application, it should berecognized by those of skill in the art that these modules are residentin software and the software may be stored, and the memory 254partitioned, as desired by the technician. Memory 254 may additionallycontain any modules shown in the exemplary embodiment of FIG. 2, andmemory 214 of FIG. 2 may contain any modules shown in the exemplaryembodiment of FIG. 5. Additionally, it is noted that, as describedabove, bit error rate measurements are inherent in sensitivity testingand thus, sensitivity test module 256 may be comprised of parts or allof test module 218.

The sensitivity module 256 adjusts the traffic type and rate, adjuststhe overall quality of the optical signal, and examines the trafficreturning from the DUT to verify that it can recover information fromit. It then varies the quality of the optical signal (the optical powerof the signal) in controlled steps for a period of time controlled bythe algorithm. Then for each step, the algorithm measures (or infers)the BER using assets within the optical testing device 100 and chooseswhether or not to make any additional steps and the details of each ofthese steps. Throughout the data recording process, the algorithmanalyzes the data. The algorithm also produces a graphical display ofthe measurement in progress and the results which may included whetheror not the DUT passes requirements input by the user.

As with the previously described exemplary embodiment, several databuses 222, 224, 226 facilitate the flow of data between themicroprocessor 210, the memory 254 and the I/O buffer 212. Another databus 228 facilitates the flow of data between the I/O buffer 212 and thecontrol bus 184. Alternatively, the data bus 228 may be deleted and theI/O buffer 212 be coupled directly to the control bus 184. Although themicroprocessor 158 is illustrated herein as including an I/O buffer 212,in an alternative embodiment of the present invention, the control unit158 provides for direct access to the memory 254 such that the I/Obuffer 212 is not required. Of course, any accessing of the memory 214in that embodiment will be monitored and/or controlled by themicroprocessor 210.

The process implemented by the sensitivity test module 256 will now bedescribed in greater detail with reference to FIG. 6. It is noted thatall of the optical components 150–158 have been energized for apredetermined duration, which permits the electronic components thereinto reach steady state. It should be noted that the sensitivity testprocedure 600 may be fully automated, whereby the technician initiatesthe process by pushing a button, which permits the control unit to fullycarry out the sensitivity test procedure 600. In this embodiment, thecontrol unit 158 will select a default error rate and a default “errorrange” within which the sensitivity must be measured. Alternatively, thesensitivity test procedure 600 may be selectively automated, whereby thetechnician may set certain parameters for the optical testing unit toimplement the test. For example, the technician may set specific powerlevels for the optical testing unit to test and may also set a specificerror range within which the sensitivity must be measured.

In any event, the sensitivity test procedure 600 begins by thetechnician initiating the procedure (step 602). This can be as simplethe technician pressing a “start button” on the graphical user interface160 all of the individual testing parameters and pushing a “start test”button. The microprocessor 210 retrieves the desired bit error rate frommemory (step 604), whether the desired BER is a default BER or a BERthat has been previously input by the technician. The control unit 158controls the optical transmitter 150 to transmit at an initial powerlevel (step 606). This may be a parameter set by the technician, or apredefined default parameter. Alternatively, the control unit 158 mayselectively control the optical attenuator 152 to increase or decreasethe amount of optical attenuation in order to output a desired opticalpower level. The optical power monitor 154 measures the output of theoptical transmitter 150 (step 608) and the optical receiver measures thenumber of bit errors at that transmitted power lever (step 610).

It is noted that the actual measured power level need not to be exactlythe same as the desired power level. In this regard, it is useful toensure that the optical testing unit accurately measures the number oferrors at the current power level. The relationship between the actualpower level and the number of errors measured at that actual power levelis important. Because the sensitivity test procedure 600 is an iterativeprocess of a finite number of iterations that seeks to determine anoptical power level at which a certain bit error rate has been achieved,the individual power level measurements which are made in order toultimately achieve the sensitivity are merely indicators of whether theoptical power level should be increased or decreased.

Accordingly, the optical receiver 156 measures the number of bit errorsat that power level (step 610). The control unit 158 then compares thedesired BER to measured BER (step 612). If it has been determined thatthe measured bit error rate is equal to the desired bit error rate (step614), the sensitivity of the DUT has been found and the control unit 158stores the current power level in memory 254 and/or outputs the currentpower level to the graphical user interface 160 as the sensitivity value(step 622). The sensitivity test procedure 600 is then terminated.

If the measured BER is not equal to the desired BER, the control unit158 then determines whether the measured BER is greater than the desiredBER (step 616). If so, the optical power level is increased (step 620)and steps 608–614 are repeated. If the measured BER is not greater thanthe desired BER, the control unit 158 decreases the optical power level(step 618) and then steps 608–614 are repeated. Although not shown, ifdesired, sensitivity procedure 600 can display sensitivity measurementsin progress to graphical user interface 160.

The sensitivity test procedure 600 provides a simple and effectivemethod for automatically measuring the sensitivity of an opticalcomponent.

In addition to determining the sensitivity of an optical component, theoptical testing unit of the present exemplary embodiment may also beused to determine whether a measured sensitivity meets or exceedsnationally or internationally recognized optical standards. Thisprovides the technician with an additional tool for comparing theparticular component to objective norms. Usefully, the “successcriteria” such as the sensitivity and the desired BER are previouslystored in memory 254, such as in standard success criteria module 258.The criteria may be downloaded into the memory 254 via a plurality ofdifferent methods, which will not be described in detail. Such methodsmay include providing external control port 101, (as shown in FIG. 1),which permits LAN interconnectivity and/or connectivity to the WorldWide Web. Other interfaces such as a CD drive, floppy disk drive orother information storage and/or input/output devices may be used toprovide a set of success criteria for each standard.

Once the success criteria are stored in memory, the procedure forcomparing the sensitivity of the optical component to standard successcriteria may be implemented as shown in FIG. 7. The standard comparisonprocedure 700 as it will be hereinafter referred to is shown in the flowdiagram on FIG. 7. It should be noted that as with the sensitivity testprocedure 600, the standard comparison procedure 700 may be fullyautomated, whereby it is automatically begun following the completion ofthe sensitivity procedure 600 or initiated by the technician simplypushing a button, and the control unit 158 fully carries out thestandard comparison procedure 700 against all known standards (e.g.,those standards stored in memory 254). Alternatively, the standardcomparison procedure 700 may be selectively automated, whereby thetechnician may input the identification for one or more standardsagainst which the sensitivity should be compared to and only thoseselected standards are compared to the measured sensitivity.

The standard comparison procedure 700 begins by the technicianinitiating the procedure (step 702). As mentioned above, this can occurautomatically upon completion of the sensitivity procedure, can be assimple as the technician pushing a “start button” on the graphical userinterface 160, or can start by the technician setting forth all of thestandards against which the sensitivity will be tested and pushing anappropriate “start button”. The control unit 158 retrieves the standardsuccess criteria from memory 254 (step 704). The control unit 158 thencompares the success criteria for a standard to the measured sensitivityand desired BER (step 706). The optical testing unit then determineswhether the sensitivity and desired BER meet or exceed the successcriteria (step 708) for that standard. If so, the control unit 158stores the positive test result in memory 254 (step 710), or optionallyoutput the result to the graphical user interface 160 (step 712), orboth.

Alternatively, if the sensitivity and the desired BER do not meet orexceed the success criteria for that standard, the control unit 158stores test failure results in memory 254 (step 714) and optionallyoutputs the test failure result to the graphical user interface 160(step 716). The control unit 158 then determines whether there are morestandard success criteria against which the DUT's sensitivity should becompared (step 718). If so, the control unit 158 advances the comparisonto the next set of success criteria (step 720) and continuously repeatssteps 708–718. After all of the comparisons are complete, the standardcomparison procedure 700 is then terminated.

The standard comparison procedure 700 provides a tremendously powerfultool for the technician by specifically outputting which standards theoptical DUT has passed and which it has failed. Via the output controlinterface (101) the optical testing unit can also provide an output suchthat a “sticker” or success report may be printed out and kept with eachoptical component under tests. This further enhances the ease of use ofthe optical testing unit.

It is noted that the steps set forth in the sensitivity test procedure600 and the standard comparison procedure 700 may vary from the orderset forth in FIGS. 6 and 7, respectively. For example, step 604 mayoccur after step 606. Those of skill in the art would clearly recognizethat there is flexibility in the ordering of some of these steps.Additionally, some steps, (such as steps 714 and 710) may be foregone,whereby the results of the standard comparison procedure 700 are notneeded to be stored. These and other variations of the illustrativeprocesses will become apparent to one of ordinary skill in the arthaving had the benefit of the present disclosure.

Referring to FIG. 8, the graphical user interface 160 is shown ingreater detail. Preferably, the graphical user interface 160 comprises atouch-sensitive screen 130 which will change depending upon thegraphical buttons 132–140 which are selected. Alternatively, thegraphical user interface 160 may comprise a CRT screen and associatedmouse (not shown) for selecting the different options on the screen.

In order to make the optical testing unit as user friendly as possible,the bottom portion of the screen 130 preferably includes a discreteselection option (i.e., hereinbefore “button”) for each of thetransmitter 132, the receiver 134, the attenuator 136, the power monitor138, and a separate button for the calibration procedure 140 and thetest procedure 142. Of course, those of skill in the art should realizethat more or fewer buttons 132–142 (such as buttons for the sensitivityprocedure 600 and the standard comparison procedure 700) or hardwiredbuttons, may be provided as desired by the user in order to implement orcontrol certain functions that are commonly used.

In operation, one of the buttons, 132–142 is selected, for example, thetest button 142 as shown FIG. 8, to initiate the desired function. Thiswill implement the test procedure 400 as hereinbefore described. Thetest results as output in steps 412, 416 may also be displayed on thescreen 130.

The invention being thus described, it would be obvious that the samemay be varied in many ways by one of ordinary skill in the art havinghad the benefit of the present disclosure. Such variations are notregarded as a departure from the spirit and scope of the invention, andsuch modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims andtheir legal equivalents.

1. A method for measuring bit error rate of an optical componentcomprising the steps of: measuring a power level of an optical outputsignal of an optical transmitter; if said power level is not a firstpredetermined power level, adjusting said optical output signal untilsaid power level is said first predetermined power level; transmittingsaid optical output signal at said first predetermined power level to anoptical device under test (DUT); receiving an optical input signal fromsaid DUT; counting a number of bit errors received in said optical inputsignal; and changing said first predetermined power level to a secondpredetermined power level and repeating at least said measuring step,said adjusting step, said transmitting step, said receiving step andsaid counting step.
 2. A method as in claim 1, wherein said adjustingstep comprises attenuating said optical output signal.
 3. A method as inclaim 1, wherein said adjusting step comprises adjusting said opticaltransmitter.
 4. A method as in claim 1, wherein said method isautomated.